ВУЗ:
Составители:
Рубрика:
TEXT 4A
COMPUTER GENERATIONS
The first generation (1951-1959). The first generation of computers is usually
thought of as beginning with the UNIVAC I in 1951. First-generation machines used
vacuum tubes, their speed was measured in milliseconds (thousandths of a second), and
the data input and output was usually based on punched cards. First-generation computers
typically filled a very large room, and were used primarily for research.
In early 1951 the first UNIVAC-1 became operational at the Census Bureau. When it
displaced IBM punched card equipment at the Census Bureau, Thomas J. Watson, the son
of IBM’s founder reacted quickly to move IBM into the computer age. The first computer
acquired for data processing and record keeping
1
by a business organization was another
UNIVAC-1, installed in 1954 at General Electric’s Appliance Park in Louisville,
Kentucky. The IBM 650 entered service in Boston in late 1954. A comparatively
inexpensive machine for that time, it was widely accepted. It gave IBM the leadership in
computer production in 1955.
In the period from 1954 to 1959, many businesses acquired computers for data
processing purposes, even though these first-generation machines had been designed for
scientific uses. Nonscientists generally saw the computer as an accounting tool, and the
first business applications were designed to process routine tasks such as payrolls
2
. The
full potential of the computer was underestimated, and many firms used computers
because it was the prestigious thing to do. But we shouldn’t judge the early users of
computers too harshly. They were pioneering in the use of a new tool. They had to staff
their computer installations with a new breed of workers, and they had to prepare
programmes in a tedious
3
machine language. In spite of these obstacles, the computer was
a fast and accurate processor of mountains of paper.
The second generation (1959-1964). The invention of the transistor led to computers
that were both smaller and faster. During this period they were about the size of a closet,
and operated in microseconds (millionths of a second). Internal memory was magnetic,
and magnetic tapes and disks as well as punched cards were used for input, output, and
storage. Computers were still fairly specialized: although computers could now be used for
business as well as scientific applications, one computer could not perform both tasks.
The computers of the 2
nd
generation which began to appear in 1959, were made smaller
and faster and had greater computing capacity. The practice of writing applications
programmes in machine language gave way to the use of higher-level programming
languages. And the vacuum tube, with its relatively short life, gave way to transistors that
had been developed at Bell Laboratories in 1947 by John Bardeen, Willliam Shockley,
and Walter Brattain.
The third generation and beyond. There is general agreement that the third
generation began in 1964 with the introduction of the IBM System 360, which could
handle both scientific and business computing. Computers shrank to the size of a large
desk, and processing time shrank to nanoseconds (billionths of a second). Instead of
individual transistors, as in the second generation, third-generation computers used
integrated circuits, or ICs, which combined hundreds or even thousands of transistors on a
Страницы
- « первая
- ‹ предыдущая
- …
- 19
- 20
- 21
- 22
- 23
- …
- следующая ›
- последняя »
